LA-ICP-MS U-Pb dating of detrital zircons from the Upper Permian Gequ Formation on the southern margin of the East Kunlun Mountains and its tectonics implications

The Upper Permian (Lopingian) Gequ Formation on the southern margin of the East Kunlun Mountains is composed of conglomerates, sandstones and calcareous mudstones of fan delta-sea carbonate plateau. It is of important significance for the analyzing of regional tectonic evolution. This paper reports the detrital zircon ages for sandstone from the Gequ Formation in the area north of Huashixia. The sandstone sample has ages of 412~2448Ma, which can be mainly divided into four age ranges, i.e., 1869~1602Ma, 1396~1270Ma, 1197~877Ma and 572~412Ma. The age ranges indicate that the source regions of the Gequ Formation experienced complex multi-phase geological events, which included the Early Paleoproterozoic tectono-magmatic event, Late Paleoproterozoic assembly event, Mesoproterozoic rifting event, Late Mesoproterozoic-Early Neoproterozoic tectono-magmatic event and Late Neoproterozoic-Early Paleozoic rifting-extension-assembly event. Magmatic rocks formed during Late Neoproterozoic-Early Paleozoic constituted the main provenance of the Gequ Formation. According to the detrital zircons ages, basin of the Gequ Formation was a"cold basin"similar to foreland basin. Contrast to the Upper Permian, there were many >2000Ma ages in the Lower-Middle Permian, and the dated zircons yielded Hercynian-Indosinian ages, which was first found in the Lower Triassic. The two significant changes were the sedimentary response to the unconformities between Upper Permian and Lower-Middle Permian, Lower Triassic and Upper Permian and the tectonic events represented by them, exhibiting a good tectono-depositional coupling relationship.